The present invention relates generally to a stereo imaging unit or system, and more particularly to a compact stereo imaging unit or system capable of phototaking stereo images having a large angle of view in the horizontal direction.
So far, a camera capable of real-time phototaking two images having parallaxes juxtaposed in the left-and-right direction for the same subject has been known in the art. Since an oblong image pickup plane is usually used for phototaking, it is general that two images are arranged side by side in the left-and-right direction. However, when it is desired to obtain horizontally long stereo images with such a phototaking arrangement, two horizontally long images must be arranged in the horizontal direction, resulting in a useless space on the image pickup plane. For instance, when two such images are simultaneously picked up by means of a single image pickup device for range finding or the like, it is difficult to obtain detailed image information.
To solve such a problem, patent publication 1 comes up with a stereo imaging optical system for capturing stereo images on an oblong image pickup plane in the vertical direction.
In this optical system, a film plane is vertically divided into upper and lower areas, as shown in FIGS. 1 and 2 of patent publication 1, and left and right images having parallaxes are guided to the upper and lower areas of the film plane by ways of two reflecting surfaces for each.
FIG. 7 of patent publication 1 also shows a small-format, wide-angle stereo imaging optical system designed as a retrofocus type by locating a negative lens on the subject side.
Patent Publication 1
JP(A)8-171151
However, the phototaking optical system set forth in this publication 1 is designed exclusively for photographic film purposes; when it is used with an image pickup device having a small image pickup plane, no sufficient angle of view is obtainable, neither is any angle-of-incidence dependence specific to the image pickup device obtained.
When the optical path for the phototaking optical system is taken apart, the left and right optical systems are broken down into independent optical systems, and so it is difficult to reduce the number of lens components involved.
Besides, the phototaking optical system of patent publication 1 has a specific construction wherein the image plane is positioned on the operator side. For this reason, the size of the optical system remains large in the depth (incident) direction, as viewed overall.
With the phototaking optical system set forth in patent publication 1, it is difficult to reduce the number of lens components involved, because when an optical path is taken apart, the left and right imaging optical systems are broken down into independent optical systems.